The present invention relates to a multicomponent fibrous nonwoven structure and the process and apparatus for producing the same. More specifically, the present invention relates to a process for forming nonwoven materials using a forming chamber in conjunction with multiple fiber sources and a forming surface to create multicomponent nonwoven materials with varying features. The materials so produced are suitable for use in a wide variety of applications including personal care products such as diapers, feminine pads and adult incontinence products.
The developments in nonwoven technology have made tremendous strides over the past two to three decades. Today there exists a wide variety of technologies for forming nonwoven materials. Examples of such technologies include meltblowing, spunbonding, meltspinning, solution spinning, carding, meltspraying and wet/dry air laying. Many of these technologies are used individually to form single component materials. As an example, spunbonding is used to form nonwoven materials which can be used in such articles as work wear and personal care products including diapers. Meltblowing can be used to generate fine pore structures adaptable for such uses as filter media and absorbents for oil and other liquids. Air laying can be used to form such products as fibrous wood pulp batts for use as absorbents in diapers and sanitary napkins. In all such cases a particular technology is used to create the particular item.
In addition to single technology materials, various technologies can be combined to create multicomponent materials. An example of this is a spunbond/meltblown/spunbond material such as disclosed in the commonly assigned patent to Brock, et al. (U.S. Pat. No. 4,041,203). This material is generally regarded as a laminate which has found uses in a wide number of areas including wipers, surgical gowns and surgical draping. In still other applications, certain technologies are combined to bring the advantages of two different forming technologies into one product. An example of such a material is described in the commonly assigned patent to Anderson, et al. (U.S. Pat. No. 4,100,324) which describes what is referred to as a coform material. This material is a combination of wood pulp fluff and meltblown fibers which are added to the fluff mixture from ancillary sidestreams as the fluff is deposited onto a forming surface such as a foraminous wire. All of these technologies and their combinations while having particular advantages also have certain disadvantages and limitations. It is therefore an object of the present invention to provide a new process and apparatus for forming nonwovens made from combinations of various technologies.
One area where the present invention is particularly well suited is with respect to the generation of fluid absorbent materials which include wood pulp fluff as one of the components. The mechanical stress and fluid handling requirements of absorbent products sometimes require the presence of bonding agents, adhesives or entangled fibers within the absorbent core to provide integrity to the product as well as to deliver and maintain the fluid functionality benefits. Anderson et al. (U.S. Pat. No. 4,100,324) teaches a method of uniformly mixing meltblown fibers in a fiberized pulp stream to produce a coform web which possesses greater strength and less dusting than pure pulp. Insley (U.S. Pat. No. 4,755,178) and Weisman (U.S. Pat. No. 4,773,903) also teach methods to produce mixed products containing blown fibers which are used to entangle other fibers or particulate materials. The addition of the meltblown fibers adds integrity to the fluff structure, however, the problem with producing this type of structure is that the material must be made on a base machine. Once the material is made, it must be slit, rewound and then transported to a mill to be converted into a finished product such as a diaper, feminine pad or incontinence garment. This activity can have an adverse effect upon the formed web simply due to the handling and processing of the finished roll. Furthermore, a high level of meltblown material within the web is generally needed to hold the structure together so that it can survive the trimming, transporting and converting operations. In addition, forming off line can result in waste due to the trimming process which is unavoidable due to the lack of control in the formation process itself. It is therefore another object of the present invention to provide a process which will reduce the aforementioned problems. The present invention provides a way to add continuous thermoplastic fibers to an absorbent composite web directly on a converting line thereby bypassing the trimming, rewinding, slitting and transportation steps. In addition, lesser quantities of the reinforcing fibers can be utilized in the finished product because the composite web is immediately converted into a finished product and therefore does not have to withstand the rigors of transportation and processing as previously mentioned.
Another problem for certain formation processes involving wood pulp fluff absorbents stems from the need for high reinforcing fiber contents or the use of adhesives throughout the material to provide sufficient integrity. In either case such additions limit the ability to scarf the absorbent to contour or shave its exterior design. It is therefore an object of the present invention to provide a process for forming materials with integrity properties and which can still be scarfed. This is possible with the present process due to the fact that the integrity fibers can be strategically placed within localized regions of the material away from the scarfing roll, thereby providing sufficient integrity while also permitting scarfing to contour the exterior surface of the material.
Another disadvantage with certain forming processes for creating wood pulp fluff absorbent batts is the degree of dusting that occurs when forming, transporting and handling the wood pulp and resultant batt. The dusting results in wasted product as well as posing an additional cleaning problem for the work place. It is therefore an object of the present invention to provide a process which is cleaner from an operational standpoint. This is accomplished at least in part because the present process utilizes a forming chamber which contains and directionally locates the fiberized wood pulp within a discrete area. The use of such a forming chamber allows for a reduction in the amount of dusting through the deposition of the material at discrete locations either on a forming surface or directly within the intended overall product.
Yet a further object of the present invention is to provide a process which will permit the addition of further components, such as particulate matter, within an environment which is well contained due to the use of a forming chamber. While the above advantages are primarily directed to the utilization of the present process to form reinforced absorbent materials, the process is also suitable for combining multiple components including other fiber technologies such as staple fibers, continuous and noncontinuous fibers, adhesives and particulate matter to form a wide variety of materials. In addition, the process of the present invention will permit the generation of materials which have localized regions containing various fractions or mixtures of the component materials. The advantages outlined above as well as other advantages will become more apparent upon a further review of the following specification, drawings and claims.